Radiotherapy plus short-course ADT confers survival benefit in oligometastatic prostate cancer

In patients with oligometastatic hormone-sensitive prostate cancer, the combination of stereotactic body radiotherapy (SBRT) plus a short course of androgen deprivation therapy (ADT) appears to improve progression-free survival (PFS), according to the phase II RADIOSA trial.

RADIOSA included 105 patients with adenocarcinoma of the prostate, biochemical progression after radical local prostate treatment, nodal relapse in the pelvis, extra-regional nodal relapse, bone metastases at next-generation imaging with a maximum of three lesions, and Eastern Cooperative Oncology Group performance status 0–1.

The patients were randomly assigned to undergo SBRT alone (n=52) or in combination with 6 months of ADT (n=53). SBRT was administered at 30 Gy in three fractions every other day or equivalent regimens depending on disease site location. For ADT, a luteinizing hormone-releasing hormone analogue was given within 1 week before the start of SBRT.

The primary outcome was clinical PFS, assessed in a modified intention-to-treat population. There were three patients lost to follow-up, leaving 51 patients in each group assessed for the primary outcome. The median age of the patients at study enrolment was 70 years.

Over a median follow-up of 31 months, the median clinical PFS was significantly longer in the SBRT plus ADT arm than in the SBRT arm (32.2 vs 15.1 months; hazard ratio, 0.43, 95 percent confidence interval, 0.26–0.72; p=0.0010).

As for safety, one patient in the SBRT arm had a gastrointestinal grade 1 adverse event (AE), and one in the SBRT plus ADT arm had a genitourinary grade 3 AE (left ureter stenosis). No late toxicities were reported. A total of 22 grade 1 ADT-related AEs occurred, all of which had resolved at the last follow-up. No treatment-related deaths were documented.

The findings warrant additional research to determine the optimal duration of ADT and identify biomarkers predicting response to SBRT alone.